1. Field of the Invention
The present invention relates to a foldable wing or airfoil, which is especially but not exclusively adapted for a projectile, and which incorporates interengaging telescopable fin sections.
2. Discussion of the Prior Art
A foldable wing or airfoil having fin sections engaging so as to be telescopically retractable into one another is disclosed in U.S. Pat. No. 4,364,531. In that instance, the foldable wing consists substantially of a front segment and a rearward segment hinged together and held opposite each other in a sliding guide extending along the outer wall of a fuselage or airborne body. The fin sections extend between the front segment and the outer wall of the body, interengaging transversely of the longitudinal axis thereof. For effecting expansion of the wing, with the segments initially abutting extended along the fuselage, a balloon located within the box-shaped fin sections is inflated from a gas supply; so as to, through the super-pressure produced in the interior, urge the box-shaped fin sections apart and thereby extend the jointed segments from the fuselage until the appropriately profiled leading edge of the rear segment, upon erection thereof, will in a rectilinear manner seal the extended fin sections along the trailing wing side. A configuration having shaped fin sections which are expanded transversely of the longitudinal axis of the projectile by internally generated superpressure for effecting the lateral movement of the segments which are initially extended along the projectile fuselage is, however, extremely space-consuming. Moreover, the freedom of the foldable wing from any interference during expansion of the wing is not completely satisfactory inasmuch as, shortly prior to the positioning of the rear segment in the final position there, there are encountered unfavorable force-introduction lever ratios, and the procedure of engaging into the operational position is additionally hindered by the increasing dynamic pressure acting on the front segment.
Even more space-consuming is the construction of the folding airfoil system disclosed in U.S. Pat. No. 4,106,727. The fin sections or channels which interlock or telescopingly interengage pairedly represent the lengthier or longitudinal sides of acute-angled triangles, the applicable bases of which triangles are defined by the expanse or extent between the channel hinges in the fuselage of the airborne body. In order to satisfy the required kinematics, it is necessary to provide sliding guides between the interlocking or interengaging channels or fin sections, (which guides are prone to operational problems) in the regions of the apex of the triangle opposite the base. The lengthy overlapping channels generate high friction moments during the unfolding of the airfoil or wing; with kinematically unfavorable forces being introduced therein during the unfolding through an adjusting member; thereby necessitating the provision of considerable additional space in the airborne body fuselage or projectile behind the channel hinges.